RRD is a terrible format. It's not compact, quickly becomes a burden when you have lots of cardinality, there's no metadata, HA is a joke and visualisation tools are basically non-existent. You basically need a whole set of extra tooling for metadata, visualisation, HA, querying to come even close to anything usable.

If RRD wasn't so terrible there wouldn't have been a myriad of replacements.